Environmental DNA (eDNA) is a newly emerging and rapidly expanding survey tool particularly within freshwater ecology but also within studies of the terrestrial environment. The aquatic eDNA survey method makes use of DNA that has become separated from its source organism and suspended in the water column. This DNA is then collected as part of a bulk environmental sample: the DNA is then isolated and extracted from the bulk sample, before being analysed for the presence of a target species.
In 2014, the method was approved for use in commercial great crested newt (Triturus cristatus) surveys within England and Wales, a species protected under both UK and EU law. eDNA has the potential to increase accuracy and reduce the cost of commercial surveys for great crested newts. However, a number of questions surrounding the use of the technique still need to be resolved. These include: (1) What are the limits of detection when dealing with very small newt populations or populations occupying large water bodies?; (2) What is the most efficient protocol for collecting samples for eDNA analysis?; (3) How does eDNA concentration vary over the newt survey season?; (4) How long does eDNA persist in the water after newts have left the pond and what are the correlates of persistence?
As part of my PhD project I am looking for answers to the questions surrounding detectability, particularly of small populations, as well as measures to increase detection rate. I am also looking at how eDNA detection changes across a season to demonstrate whether the technique is usable outside the standard great crested newt survey window. In addition to these questions, I am also attempting to identify an index of abundance of great crested newts from eDNA sample data. As part of this project, I am using a naturally colonised, replicated pond system, where newts have been monitored for 16 years and the exact numbers of newts in each pond are known throughout the season, as well as natural ponds.
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